In U.S. Pat. No. 2,827,075 a servo pressure regulator valve is proposed; however, the proposed construction does not render the same readily applicable to thermal management systems by virtue of the non-hermetic sealing of the valve casing. Moreover, the proposed valve construction includes a number of individual components many of which are in sliding engagement and/or are fashioned of a material which limits not only the application of the proposed valve structure but also the service life thereof.
In U.S. Pat. Nos. 3,556,128 and 3,493,008, pressure balanced regulating valves are proposed; however, the proposed valves are two stage regulating valves requiring an external pilot valve. Additionally, the proposed valves require a considerable number of sliding components resulting in not only affecting the service life of the valve but also providing more occasion for a possible malfunctioning of the overall valve structure.
Likewise, in U.S. Pat. No. 4,617,958, a multi-function pressure regulation control valve is provided which includes a number of individual components many of which are in a sliding fit in addition to a number of individual seals. The proposed multi-function valve is controlled or actuated by external electric signals and, by virtue of the number of components and sliding fits, the proposed valve construction is subject to possible malfunctioning as well as a shortened useful life.
U.S. Pat. No. 4,682,622 proposes a self-powered pressure regulating valve constructed as a delta pressure regulator; However, one disadvantage of this proposed construction resides in the requirement for external lines for a pressure sensing.
U.S. Pat. No. 4,619,115 proposes a backpressure regulating valve; however, a disadvantage of this proposed valve resides in the fact that the valve is not self-powered and is somewhat complicated in construction.